Alkylation reactions generally involve contacting a first aromatic compound with an alkylation agent in the presence of a catalyst to form a second aromatic compound. One important alkylation reaction is the reaction of benzene with ethylene in the production of ethylbenzene. The ethylbenzene can then be dehydrogenated to form styrene.
Catalyst life is an important consideration in alkylation reactions. There are the costs related to the catalyst itself, such as the unit cost of the catalyst, the useful life of the catalyst, the ability to regenerate used catalyst, and the cost of disposing of used catalyst. There are also the costs related to shutting down an alkylation reactor to replace the catalyst and/or to regenerate the catalyst bed, which includes labor, materials, and loss of productivity.
Catalyst deactivation can tend to reduce the level of conversion, the level of selectivity, or both, each which can result in an undesirable loss of process efficiency. There can be various reasons for deactivation of alkylation catalysts. These can include the plugging of catalyst surfaces, such as by coke or tars, which can be referred to as carbonization; the physical breakdown of the catalyst structure; and the loss of promoters or additives from the catalyst. Depending upon the catalyst and the various operating parameters that are used, one or more of these mechanisms may apply.
Another cause of catalyst deactivation can be the result of poisons present in an input stream to the alkylation system, for example amine or ammonia compounds. The poisons can react with components of the catalyst leading to deactivation of the component or a restriction in accessing the component within the catalyst structure. The poisons can further act to reduce yields and increase costs. Therefore, a need exists to develop an alkylation system that is capable of reducing alkylation catalyst deactivation or a method of managing alkylation catalyst deactivation in an effective manner. It is desirable to reverse the effect of catalyst deactivation and reactivate alkylation catalyst that has experienced deactivation.
In view of the above, it is desirable to have an effective method to produce ethylbenzene in commercial quantities via a catalytic alkylation reaction with reduced or no catalyst deactivation. It would further be desirable if the method was capable of reversing the effect of catalyst deactivation and reactivate alkylation catalyst that had experienced deactivation without the need to take the catalyst out of service for regeneration or replacement procedures.